Why would you fight crime with a sai, when a gun is deadlier, and in many cases, more legal?
Because guns make noise. A sai is a ninja weapon, and silence, theatricality, being deadly are what ninjas in comics are about.
Why doesn't Superman have a utility belt...
He has a compartment in his belt buckle that's shielded and can hold a kryptonite ring.
More important, however, he rarely needs anything. He can move fast enough and with enough precision that he can act as any tool he needs. See heat vision for a lot of fine tuning work. His senses cover any scanning he needs to do. This is the opposite of a hero who would need anything.
why doesn't Batman wear his anti-Kryptonian battlesuit more often?
He's a ninja. Could you sneak around, crawl in ventilation shafts, or convince people you are a living bat-monsters of the shadows, wearing a giant suit? It's clunky.
If he was going to do that, he'd be Iron Man; who isn't, I might add, the hero for the job of the criminals Batman has to deal with. Nor a Mystery Man detective.
How is a person who can split into three people any more useful than any given three people who are not special forces ninjas?
communication. And if this is the one from Legion, special training as well. And she's not "normal", compared to a bystander like a taxi driver or a hot dog vendor, or an office mook. She's got moxy to be a hero.
Why are there any cyborgs left alive in the Marvel Universe when they could so easily be killed with high energy microwave weapons?
Carry a microwave around for a day. All day. No putting it down. Heavy, eh? Well, that's why.
Better question: why are there so many humans when they can be killed by... anything!!! A gun is the tip of the iceberg.
If a Cyborg can only be killed by a microwave, that's awesome: 99.9% of weapons are not high energy microwave weapons. There aren't even superheroes who use Microwaves, at least not many, and they may not even be working this particular case.
The costumes are there because they accent the human form. It's a great excuse to draw naked people, just like the renaissance. They're not naked, but they are. I have drawn comics, and while I don't do genitalia, I do do (sorry) everything leading up to that before drawing in the lines of even armor or equipment.
Not sex, mind you, but the human form. And it's okay, and no one feels ashamed of themselves, and no one even notices how really naked everyone really is. Weird, right?
Comics are also about power fantasies. Note how everyone looks awesome, with bodies that blow your/my mind, and they are super strong, and smash things, and explode with energy. There are a lot of billionaires (used to be millionaires, but now it's Billionaires), and scientists who make other scientists look like idiots. Lots of non-power characters who just cannot lose (and for no good reason, either; especially sucker-punching Thor or Superman to drive home this point). Lots of flying, and a fight in every. single. comic.
I suppose there's a thing about powers or equipment. Only the Rob Liefield creations really crossed that line for protagonists (at least in a loud way), with Cable and Deadpool using gear. Excluding cybernetics, of course (ie: wolverine's claws).
Anyway, sounds like you've never gone 4-color.